Book ReviewsOrigins & Design 18:1

Full House Follies

This little book is intended to
correct the popular impression that "progress and increasing
complexity" are characteristics of life's course on Earth.
Progress has, in the twentieth century, already been punched silly;
but paleontologists seem genuinely more complex than paramecia,
a point that Gould concedes, if only for reasons of professional
pride. His doubts arise whenever the twig of a trend is taken
as typical or representative. The underlying error evidently runs
deep. "[W]e are still suffering," he writes, "from
a legacy as old as Plato, a tendency to abstract a single idea
or average as the 'essence' of a system, and to devalue or ignore
variation among the individuals that constitute the full population"
(40).

If essentialism is the affliction, evolution is the remedy.
"Darwin's revolution," Gould believes, "should
be epitomized as the substitution of variation for essence as
the central category of natural reality," (42). The revolution
complete, there will be individuals and their variances out there
where the central categories lie. Nothing else. This seems for
all the world like nominalism, a doctrine current in Twelfth century
Paris, where Abelard may be seen stealing kisses from Heloïse,
drab Darwin dutifully waiting his turn at bat. Gould is off by
centuries; his essential quarrel, of course, is with Aristotle
and the doctrine of real essences.

No matter, I would ordinarily say, drawing down the curtain
of charity. Like paleontology, philosophy is an acquired taste.
But having been tempted by philosophy, Gould is tempted again
by statistics, prompting me to yank that curtain up again. Witness
thus his discussion of normal distributions, the familiar bell-shaped
curve. "We regard the normal distribution as canonical,"
Gould writes, "because we tend to view systems as having
idealized 'correct' values, with random variations on either sideanother
consequence of lingering Platonism" (52).

I am afraid that Plato, poor pooch, has nothing to do with
it. Whatever the Form of the Good may be, it is not constructed
by counting noses. We regard the normal distribution as canonical
because it is canonical, a fact readily demonstrated in elementary
texts, the distribution of distributions itself following a bell
shaped curve. Perhaps that curtain had better stay up. Although
drawn incorrigibly to the Big Picture, the focal plane of Gould's
attention is best adapted to short distances. Ted Williams was
the last of the big-time hitters, his 1941 record now receding
into memory and myth. Why should this be, Gould asks? It is not
clear that in a world bursting with sin and suffering this question
cries out for an answer, but the question illustrates a trend,
and trends are what tend to interest Gould.

The disappearance of the four-hundred hitter might suggest
that in baseball, as in so much else, things have gotten worse.
In fact, Gould argues, play has in general improved, those rumpy
players now scampering across the field better-conditioned and
surely better-paid than their stubble-chinned predecessors. It
is this circumstance, curiously enough, that provides Gould with
an answer to his question.

What follows as the standard of play improves? Nothing on average,
better hitters encountering better fielders, their simultaneous
improvements canceling one another. But athletic performance is
bounded by a wall marking the limitations of the human body. Batters
may hit so far, and no further; there are some balls that no ballboy
ever shags. The wall stands to the right of the bell curve measuring
athletic performance like the north face of Anapurna, grim, forbidding
and uncrossable. As play improves, the bell curve shifts itself
closer to the wall. Variations shrink, the right tail of the curve
steepening. Without such steepening, the curve would cross the
wall into the forbidden zone. The disappearance of the four-hundred
hitter now follows inexorably, if only because his room for maneuver
has been vacated, the batter squeezed between better competition
and the wall.

This is an elegant analysis, but one that tempts Gould anew
into the badlands of metaphysics. "Hitting 400," Gould
concludes, "is not a thing, but the right tail of the full
house for variations of batting averages." With this, who
would quarrel, but then who has ever been persuaded that a batting
average is a thing? The assimilation of a very particular batting
average to the full house of variations is a mistake as well.
An average is a number; the full house a curve embodying a multitude
of points and so a continuum of numbers. Trends arise when specific
points on the curve are tracked.

Gould has confused the shadow of one distinction for the substance
of another. If he could have continued to play unaged, Ted Williams
would have seen his batting average drop year by year, even though
he stood forever in the sunshine of his youth. Batting averages
are relative to the circumstances of play. In this, a man may
be diminished without changing, his relative decline nonetheless
marking a real trend. Not so in the case of height or weight.
No man becomes fat because other men have grown thin. It is this
distinction between relative and absolute properties that is the
cynosure of Gould's concerns. The contrast between variations
and trends that Gould means to collapse remains healthy as a horse.
"Darwin's revolution will be completed," Gould writes,
"when we smash the pedestal of human arrogance and own the
plain implications of evolution for life's nonpredictable non-directionality"(29).
A great many biologists seem keen to smash that pedestal, seeing
forever an ape's haunted eyes peering from every human face; but
the more that Darwinian thought shows that life is going nowhere,
the less it explains about where life has gone, the net effect
akin to division by zero. Writing about the evolution of the horse,
Gould juxtaposes evolutionary fable to the fossil record. High
school textbooks propose that, desiring an increase in stature,
the rabbit-sized Eohippus (but not curiously enough, the rabbit-sized
rabbit), commenced his move up through the evolutionary ranks,
one incremental step after the other. This might suggest a trend,
the familiar museum displays showing the beasts getting bigger
and better, with even their coats becoming glossier over time.

The fossil record shows something different: rather a thick
bush, with horse-like species entering the record at one time,
leaving it at another. The high school progression is an artifact;
a great many intermediates are absent from the record, their trace
only a doleful dotted line. The facts are discrete. There is no
hint of gradual change, no hint either of selective advantages
accumulating. "Throughout the history of horses," Gould
recounts (quoting Prothero and Shubin's well-known monograph),
"the species are well-marked and static over millions of
years."

All this confirms Gould in his conviction that variations are
crucial and trends an epiphenomena; but having in this case destroyed
the notion of an evolutionary progression, Gould runs the risk
of destroying the notion of an evolutionary explanation as well.
The stratigraphic charts make the heresy irresistible. There is
variance, to be sure, but no change in variance, and so no evident
trend. Why imagine that there is anything to the record beyond
what one seesone damn horse after the other? If the horses are
going nowhere, not so the Foraminfera--single-celled creatures,
protozoa, in fact, that popped into existence at the beginning
of the Cretaceous some 136 million years ago. Starting out small,
some species increased in size, at least until an obliging mass
extinction served to reduce the population, with essentially the
same story replayed during the earlier and later Cenozoic eras.
The statistics reflect a bell-shaped curve, but one that is skewed
in the directing of increasing size.

An effect demands a cause. Why the skewing? The classical Darwinian
explanation involves a trip of three steps: random variations,
followed by natural selection, followed in turn by biological
change. Gould proposes to cut out the middleman entirely, moving
from random variations to biological change wholesale.

What is given, then, are Foraminfera with an inherent variability,
a repertoire of potential changes. As the Cretaceous commences,
they are, those protozoa, collected by a wall marking the lower
limits of their size. Thereafter, they simply drift, taking themselves
to whatever place their variations allow. The wall functions to
enforce a principle of elastic reflection; as protozoa hit the
wall, they bounce forward. This serves to impart a preferred direction
to their drifting, the simple structure of a stochastic set-up
producing a simulacrum of a trend. Some species get bigger over
time simply because they have the chance. "Size increase,"
Gould writes, "is really random evolution away from small
size, not directed evolution toward large size" (162).

Such is Gould's theory of expanding stochastic variation. It
is a theory that suggests again to Gould the enduring reality
of variations, the trends in this case arising from a failure
to properly distinguish passive from driven systems. The driven
systems move forward with a vengeance, natural selection on the
classical view positively hustling species over an adaptive landscape;
the passive systems just sit there and drift. This distinction
seen, trends tend to dwindle and disappear, leaving behind only
the Foraminfera, smiling enigmatically, like so many cats. Does
the combination of drift and bounce suffice in the case of Foraminfera
to explain their increase in size? We cannot be sure. Size has
been measured by a single numerical parameter; this lends a false
plausibility to a picture of driftfalse because lacking analytical
precision. Foraminfera never become large as whales. Their variations
are bounded. How so? And by what? The mechanism of variation that
allows Foraminfera to increase in size, too, is left largely in
the dark, with no coordination drawn between what the Foraminfera
do and how they do it. The statistical pattern that Gould sees
among the Foraminfera he sees again in life as a whole. There
is no progress in the evolutionary record; indeed, no overall
trends. Life is dominated by bacteria, the little bugs slithering
through every interstice and filling every conceivable crevice,
the bacterial mode remaining unchanged over time, stable as a
rock and about as interesting. There is, Gould acknowledges, the
fact that "the most complex creature has tended to increase
in elaboration through time," (169), but increasing complexity
reflects nothing more than the same pattern seen locally among
the Foraminfera as they increase in size. The mean measuring complexity
increases, the mode does not; whatever trends are tending reflect
"changes in variation rather than things moving somewhere"
(168).

By now the point has become familiar while remaining unpersuasive,
like an advertisement for breakfast cereal. The provocative and
plausible part of Gould's thesis lies elsewherewith the idea of
expanding stochastic variation. But where the doctrine is plausible,
as in the case of Foraminfera, it is not provocative, and where
provocative, not plausible.

Looking backwards some 3.5 billion years, Gould observes bacteria
crouched by an initial wall, one marking what he calls "minimal
complexity." Movement away from the wall is movement toward
increasing complexity. "As life diversified," he writes,
"only one direction stood open for expansion" (171).
Some species have grown progressively more complex; but "the
vaunted progress of life," Gould writes with satisfaction,
"is really random motion away from simple beginnings, not
directed impetus toward inherently advantageous complexity"
(173).

In coming to this conclusion, Gould has been misled by his
own analogy between size and complexity. Both increasing size
(among Foraminfera) and increasing complexity (in life) yield
right-skewed distributionsbell-shaped curves with long right tails.
Such is the statistical picture, but it is a picture that describes
as well the distribution of height in human habitation since the
fifteenth century. Most buildings have remained small, some have
gotten bigger; and no one imagines that taller buildings arise
because they have simply "wandered into a previously unoccupied
domain." This is a point to which Gould is sensitive, but
the statistical tests that he invokes to distinguish passive from
driven systems seem to me far too coarse to be of interest.

Expanding stochastic variation may well carry the Foraminfera
to an increase in size; the problems associated with complexity
are of a different order entirely. Biological objects are made
of many parts and only a particular arrangement of those parts
serves to realize a biological function. A probability thresholda
wall, to continue Gould's imageseparates complex objects from
any mechanism of random search. No arbitrary rearrangement of
the eye is apt to see; no reconfiguration of the heart to pump
blood. This is to speak only at the most superficial level of
analysis. An organism comprises any number of very complex systems
coordinated to achieve a variety of familiar but poorly-described
biological functions. Even the simplest of biological systems--the
bacterial cell, in fact--suggests an exponentially increasing order
of complexity, as complex structures interact with one another
in ways that are themselves complex.

The great evolutionary trajectories span many dimensions and
relatively short periods of time. Causes evoke effects, but effects
in turn influence their causes; things are strongly non-linear
and analytically intractable. The structures that result occupy
points in a space that no mathematician has ever glimpsed, let
alone described. The examples of complexity that Gould invokes,
by way of contrast, are one dimensional and almost hopelessly
trivial, a point that with a good-natured shrug, Gould himself
comes close to acknowledging.

Gould is right to scruple at progress, but he has added his
voice late to the chorus. Everyone else has already left off shouting.
He is right again to be skeptical of traditional explanations
in biology. Richard Dawkin's The Blind Watchmaker and Daniel
Dennett's Darwin's Dangerous Idea are books in which ignorance
is made an epistemological principle. But he is wrong to suppose
that the only alternative to systems driven by natural selection
are systems that are not driven at all. Random mechanisms cannot
in principle explain the nature of biological complexity, the
doctrine of expanding stochastic variation returning evolutionary
thought to the dread place from which it has always tried to flee.
By endeavoring to deconstruct a distinction between trends and
variances, Gould has inadvertently come to express a more profound
and ultimately more explosive truth: that the issue why things
in biology change as they do remains what it has always been,
which is to say an abysmal mystery.